We were hiking in Muir Woods recently when we came across this magnificent barred owl hanging out on a branch near the trail. We had climbed up one side of a deep ravine, which brought us level with the treetop in which he was relaxing.

We stood and watched him for a few minutes in transfixed silence. Later, though, I learned that barred owls are actually an invasive species from the East Coast. They’re basically just better at being an owl than the species they’re displacing: they eat a more varied diet, have more fledglings per clutch, and are more aggressive about chasing other owls out of their territory. In Muir Woods, they’ve entirely driven out their more bashful cousin, the native spotted owl.

The barred owls have so aggressively taken over new territory that ecologists are now considering a tactic euphemistically known as “on-site lethal removal” to remove the owls from places like Muir Woods. To me, this brings up so many questions – what is an invasive species? What responsibility do we have to the native species when we bring their competitors with us? And to what ends will we – should we – go to preserve a particular ecosystem?